Vanderbilt Postdoc Kate Snyder Uncovers How Boundaries and Bonds Build Bird Song
By Andy Flick, Evolutionary Studies scientific coordinator
Female song is far more widespread in songbirds than many people realize, occurring in about two thirds of songbird species, and new research is reshaping how scientists understand its evolution. Using large-scale species-level datasets collected on songbird behaviors, Associate Professor of Biological Sciences Nicole Creanza and her lab are discovering new insights into the social factors that underlie the evolution of birdsong, especially in female birds.
Female song remains one of the most understudied and misunderstood aspects of songbird biology, and the team argues that its role may be far more complex than previously appreciated. There are nearly 5,000 songbird species, each shaped by distinct environments and social contexts. The functions of female song seem to differ across these species, and too few species-level studies exist to draw broad generalizations, though limited field evidence supports female song serving roles in territory defense, conflict mediation, pair communication, and social recognition.
Birdsong is often studied through the lens of competition among males, since many use their songs to defend a territory or compete for mates. The research team for this work, led by postdoctoral researcher Dr. Kate Snyder, used data collected from more than 1,000 songbird species to uncover the role of a less common social behavior, cooperative breeding, on the evolution of singing behaviors.
Cooperative breeding, where individuals help raise offspring that are not their own, occurs in roughly 10 to 15 percent of songbird species, likely driven by factors such as harsh environments, limited breeding resources, and the fitness benefits helpers can gain through experience, group safety, and even future reciprocal assistance.
Using phylogenetic comparative analyses, the team found that cooperative breeding was strongly associated with the presence of female song. Importantly, the relationship between cooperative breeding and female song appears to run in both directions, with each behavior reinforcing the other over evolutionary time (Figure 2).
The team investigated how territoriality interacted with this association. Creanza and Snyder note that about 28 percent of songbird species defend territories year-round, and about 72 percent actively defend territories for at least part of the year, underscoring how variable territorial behavior is across the songbird family tree. Territoriality affects both singing and breeding behaviors, so the team effectively asked “does territoriality explain the association between cooperative breeding and female song?”
They found that, while cooperative breeding and female song commonly co-occur in strongly territorial species, their association is especially pronounced in weakly territorial species, meaning those that are tolerant of intruders or have flexible territory boundaries, where the two behaviors appear together far more often than chance would predict. This pattern suggests that there may be at least two evolutionary pathways to female song: in strongly territorial species, females may sing to help defend the territory, while in weakly territorial species, female song may serve a role in promoting social cohesion within cooperative groups.
Creanza hopes the findings reach a broad audience. “We hope the public learns that female birds sing, if they did not know that already, and that social behaviors can shape evolutionary patterns.”
Talking about what drove her interest, Creanza explained, “people (and other birds!) use birds’ songs to identify their species, but I kept thinking about how to retrace birds’ songs further back in evolutionary history and disentangle the factors that influenced them.”
Snyder continued, “more broadly, sometimes phenomena happen in evolution that are not the dominant pattern or occur relatively infrequently, but are nonetheless important. Sometimes large-scale phylogenetic comparative analyses are the best or most tractable way to detect these phenomena and evaluate whether they have consistent evolutionary effects, elevating explanations of associations beyond ‘just-so’ stories.”
Citation: Snyder, K.T., Loughran-Pierce, A., Creanza, N. Territoriality modulates the coevolution of cooperative breeding and female song in songbirds. 2026. Nature Ecology and Evolution. (2026).
Funding Statement: Snyder and Creanza were funded by grants from the National Science Foundation (IOS-2327982, BCS-1918824, and DUE-1926736). Loughran-Pierce was supported by the School for Science and Math at Vanderbilt. This work was supported by a Pilot Grant from the Evolutionary Studies Initiative at Vanderbilt.